Nowadays, 4G LTE mobile networks have embedded several different transmission modes capable to strongly enhance the user's throughput. One example of such differentiation is between transmitting using SIMO mode (Single Input-Multiple Output) or MIMO (Multiple-input multiple output) mode.
MIMO (Multi-Input Multi-Output) transmission modes are supported by utilizing multiple antennas both at the receiver and at the transmitter side (access node and user equipment, UE). Depending on the number of antennas at the UE and access node sides, different throughput values can be attained by the MIMO transmission mode. Theoretically, the more the antennas, the higher the throughput. The usage of MIMO allows maximum performance but implies the utilization of at least 2 different power amplifiers in the RF part of a NodeB, (while SIMO can be handled with only one power amplifier) and when an amplifier is ON it consumes an amount of energy.
However there may be several users in a cell that do not need the very high peak rate achievable through MIMO mode of operation, and in these cases the overconsumption of energy does not make sense. Since MIMO transmission mode is more costly in terms of energy-consumption with respect to SIMO transmission mode, having an intelligent decision-making process that would apply SIMO mode when certain conditions are met would translate into a more energy-efficient network, as well as in cost savings for telecom operators. For these reasons, some solutions have been proposed in the prior art to optimize the usage of the MIMO mode only in those situations in which a difference (e.g. in terms of cell throughput and/or capacity) is found, considering the trade-off between user experience and energy/OPEX savings.
Most of the existing radio access network (RAN) solutions known so far simply consider the cell load as a parameter to decide if MIMO mode has to be enabled and thus whether a second power amplifier should be switched-on. Typical examples include tracking if in a cell there is at least one user (and accordingly use this information to switch between MIMO/SIMO modes), or deciding that in specific night hours (in which lower traffic is expected) a cell is left in SIMO mode only.
These solutions are very basic as no optimization or trade-off capability is provided to the operator. Therefore, there is a need in the art for optimizing these schemes which further improve the use of MIMO mode in telecommunication networks. The cell energy consumption should be further optimized by using additional user information available, for example, in the nodes, providing therefore a set of intelligent mechanisms that would trigger on and off the MIMO operation mode.